From patchwork Thu Oct  2 13:05:26 2008
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Subject: [22/32] netvm: filter emergency skbs.
Date: Thu, 02 Oct 2008 03:05:26 -0000
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
X-Patchwork-Id: 2406
Message-Id: <20081002131609.278132620@chello.nl>
To: Linus Torvalds <torvalds@linux-foundation.org>,
 Andrew Morton <akpm@linux-foundation.org>,
 linux-kernel@vger.kernel.org, linux-mm@kvack.org,
 netdev@vger.kernel.org, trond.myklebust@fys.uio.no,
 Daniel Lezcano <dlezcano@fr.ibm.com>,
 Pekka Enberg <penberg@cs.helsinki.fi>,
 Peter Zijlstra <a.p.zijlstra@chello.nl>,
 Neil Brown <neilb@suse.de>, David Miller <davem@davemloft.net>

Toss all emergency packets not for a SOCK_MEMALLOC socket. This ensures our
precious memory reserve doesn't get stuck waiting for user-space.

The correctness of this approach relies on the fact that networks must be
assumed lossy.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>

---
net/core/filter.c |    3 +++
 1 file changed, 3 insertions(+)

Index: linux-2.6/net/core/filter.c
===================================================================
--- linux-2.6.orig/net/core/filter.c
+++ linux-2.6/net/core/filter.c
@@ -81,6 +81,9 @@ int sk_filter(struct sock *sk, struct sk
 	int err;
 	struct sk_filter *filter;
 
+	if (skb_emergency(skb) && !sk_has_memalloc(sk))
+		return -ENOMEM;
+
 	err = security_sock_rcv_skb(sk, skb);
 	if (err)
 		return err;